The present invention relates to a power supply.
The invention has been developed primarily for use with mobile telephones and will be described hereinafter with reference to that application. It will be appreciated, however, that the invention is not limited to that particular field of use and is also suitable for other electronic devices, particularly portable devices such as Notebook computers, palmtop computers, electronic organisers, two-way pagers, remotely powered electronic device and the like.
Pulsed loads occur in many battery-powered portable devices and the peak current may be many times the resting current. When the battery is nearly flat or is old, its"" effective internal resistance tends to increase, and it is less able to supply peak current demand without the device cutting out. Heavy load pulses generally also cause a large voltage drop when they occur, and this may be detrimental to the battery. Lithium-ion batteries are particularly susceptible to damage in this way.
As a result, pulse loads invariably reduce battery run-time as the load will have a minimum threshold supply voltage required at all times. When the load pulses and that voltage drop below the minimum threshold, the electronic device must shut down as the voltage regulating circuitry is no longer able to supply the necessary voltage to run key circuits. However, at this time there may be useful energy remaining in the battery.
Moreover, some portable devices include protection circuitry that shuts the device down if the current drawn from the battery exceeds a predetermined threshold. While this circuitry is designed to protect the battery, it also results in shut down of the device when the peak current, although being over the threshold, was so for only a short period. This then requires the device to be restarted and, in some, cases, reconfigured. For mobile telephone and personal computing applications this is a source of frustration to users.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
It is an object of the invention, at least in the preferred embodiment, to overcome or substantially ameliorate at least one of the disadvantages of the prior art, or at least to provide a useful alternative.
According to a first aspect of the invention there is provided an energy storage device including:
a battery having a predetermined internal resistance R and two terminals for allowing electrical connection to the battery, and
a supercapacitor connected in parallel with the terminals and having a predetermined equivalent series resistance ESR, where ESR less than 0.25.R.
Preferably, the ESR less than 0.1.R.
Preferably also, the device supplies a load with a pulsed load profile, wherein the capacitance provided by the supercapacitor is sufficient to limit the battery current to a predetermined maximum. More preferably, the supercapacitor provides a substantially constant current as the energy storage device discharges.
In a preferred form, the device includes a housing for containing both the battery and the supercapacitor, the terminals being accessible from outside the housing for connecting to a load.
According to a second aspect of the invention there is provided a power supply for a portable electronic device, the power supply including an energy storage device according to the first aspect and supply rails for engaging the terminals of the energy storage device.
Preferably, the supply rails selectively engage the terminals. More preferably, the terminals are moved out of engagement with the supply rails to allow the like terminals of a like energy storage device to be moved into engagement with the supply rails.
According to a third aspect of the invention there is provided an energy storage device including:
a battery for providing a battery current and having two terminals for electrically connecting with a load; and
a supercapacitor connected in parallel with the terminals and having a predetermined capacitance that, in use, limits the battery current to a predetermined threshold.
Preferably, the load draws a pulsed current from the energy storage device
According to a fourth aspect of the invention there is provided a power supply including:
a battery for providing a battery current and having two terminals for electrically connecting with a load that demands a pulsed current; and
a supercapacitor connected in parallel with the terminals for maintaining the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.5.
Preferably, the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.3. More preferably, the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than 1.1.
According to a fifth aspect of the invention there is provided an energy storage device including:
a battery for providing a battery current and having two terminals for electrically connecting with a load that demands a pulsed current; and
a supercapacitor connected in parallel with the terminals for maintaining the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.5.
Preferably, the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.3. More preferably, the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than 1.1
According to a sixth aspect of the invention there is provided a power supply including:
a battery having two terminals for electrically connecting with a load that demands a pulsed current; and
a supercapacitor connected in parallel with the terminals for maintaining the ratio of the range of instantaneous power provided by the battery and the average value of the power provided by the battery at less than a predetermined threshold.
Preferably, the the predetermined threshold is one of the following: 1.5; 1; and 0.3.
According to a seventh aspect of the invention there is provided an energy storage device including:
a battery having two terminals for electrically connecting with a load that demands a pulsed current; and
a supercapacitor connected in parallel with the terminals for maintaining the ratio of the range of instantaneous power provided by the battery and the average value of the power provided by the battery at less than a predetermined threshold.
Preferably, the predetermined threshold is one of: 1.5; 1; and 0.3.
According to an eighth aspect of the invention there is provided an energy storage device including:
a battery having a predetermined internal resistance R and two terminals for allowing electrical connection to the battery, and
a supercapacitor connected in parallel with the terminals and having a predetermined equivalent series resistance ESR and a capacitance C, where ESR less than 0.5.R and C is less than 1 Farad.
According to a ninth aspect of the invention there is provided an energy storage device including:
a battery having a predetermined internal resistance R and two terminals for allowing electrical connection to the battery; and
a supercapacitor connected in parallel with the terminals and having a predetermined equivalent series resistance ESR, where ESR less than 110 mOhms less than R.
Preferably, the ESR is less than about 50 mOhms. More preferably, the ESR is less than about 30 mOhms.
According to a tenth aspect of the invention there is provided an energy storage device including:
a battery having a predetermined internal resistance R and two terminals for allowing electrical connection to the battery; and
a supercapacitor connected in parallel with the terminals and having a predetermined equivalent series resistance ESR, a predetermined volume V and a predetermined capacitance C, where ESR less than 0.5.R, V less than 14 cm3 and C greater than 1 Farad.
According to an eleventh aspect of the invention there is provided an energy storage device including:
a battery having two terminals for allowing electrical connection to the battery; and
a supercapacitor having a plurality of serial connected supercapacitor cells for connecting in parallel with the terminals, wherein the supercapacitor cells have an operating voltage of at least 2.3 Volts and the supercapacitor has a predetermined equivalent series resistance ESR of less than about 20 mOhms.
Preferably, the ESR is less than about 15 mOhms.
According to a twelfth aspect of the invention there is provided an energy storage device including:
a battery having two terminals for allowing electrical connection to the battery; and
a supercapacitor having a plurality of serial connected supercapacitor cells for connecting in parallel with the terminals, wherein the supercapacitor cells have an operating voltage of at least 2.3 Volts and the supercapacitor has a predetermined capacitance of greater than about 1.9 Farads.